Question

The way my game and server work is like this:

I send messages that are encoded in a format I created. It starts with ‘p’ followed by an integer for the message length then the message.

ex: p3m15
The message is 3 bytes long. And it corresponds to message 15.
The message is then parsed and so forth.

It is designed for TCP potentially only sending only 1 byte (since TCP only has to send a minimum of 8 bits).

This message protocol I created is extremely lightweight and works great which is why I use it over something like JSON or other ones.

My main concern is, how should the client and the server start talking?

The server expects clients to send messages in my format. The game will always do this.

The problem I ran into was when I tested my server on port 1720. There was BitTorrent traffic and my server was picking it up. This was causing all kinds of random ‘clients’ to connect to my server and sending random garbage.

To ‘solve’ this, I made it so that the first thing a client must send me is the string “Hello Server”.

If the first byte ever sent is != ‘H’ or if they have sent me > 12 bytes and it’s != “Hello Server” then I immediately disconnect them.

This is working great. I’m just wondering if I’m doing something a bit naive or if there are more standard ways to deal with:

-Clients starting communication with server
-Clients passing Hello Server check, but somewhere along the line I get an invalid message. I can assume that my app will never send an invalid message. If it did, it would be a bug. Right now if I detect an invalid message then I disconnect the client.

I noticed BitTorrent was sending ‘!!BitTorrent Protocol’ before each message. Should I do something like that?

Any advice on this and making it safer and more secure would be very helpful.
Thanks

Answer 1

perhaps a magic number field embedded in your message.

struct Message
{
    ...
    unsigned magic_number = 0xbadbeef3;
    ...
};

so first thing you do after receive something, is checking whether the magic_number field is 0xbadbeef3.